The present invention is concerned with wireless over-the-air communication using a plurality of transmit/receive cell sites or relay points. It should be understood that the transmit/receive relay points can be either land based or non-land based, such as satellite based, and that as used herein, the term "cell site" or its equivalent refers to one of the relay points of the system. CMR (Cellular Mobile Radio) is an example of one type of wireless over-the-air communication system that can be included in the present disclosure. It is understood that the term CMR is not intended to be limiting, but is merely used as an example for the purposes of discussion. It is also to be understood that the term "cellular telephone system" or its equivalents is intended to be shorthand notation for the term "wireless over-the-air communications system" and no limitation is intended by the use of the term "cellular." Also, as used herein, the terms "CD (Communication Device)" and "MU (Mobile Unit)" are intended to include any device used to communicate in the wireless over-the-air communication system. Also, the term "cellular telephone system" is used for purposes of discussion but can include any form of wireless over-the-air communication system. It is also noted that many forms of communication are and will be conducted over the wireless over-the-air networks. Therefore, the present disclosure will refer to a "communication process" which is intended to cover calls as well as other forms of communication that can be conducted in this manner.
CMR is a rapidly growing telecommunications system. The typical CMR system includes a multiplicity of cells. A particular geographic area can be subdivided into a multiplicity of subareas, with each of the subareas being serviced by a stationary transmitter/receiver setup. The cells are set up to carry signals to and from mobile units in the range of the cell. If one cell site becomes too crowded, it can be divided into smaller cells, by a process known as cell site splitting. Any particular geographic area can become quite complicated with cells overlapping each other, and overlapping cells of other neighboring cellular systems. Further, null zones with inadequate coverage, or even no coverage, can result. It is noted that the term "cellular" is intended to be a term of convenience, and is not intended to be limiting. The present disclosure is intended to encompass any communication system in which an overall area can be divided into one or more subareas, and also to any communication system having at least some portion of the communications occurring over the air.
A typical CMR set up is indicated in FIGS. 1 and 2, and will be described so an understanding of the problem to which this invention is directed can be obtained.
Shown is a typical cellular telephone unit having a unique mobile identification number stored in a suitable location such as an electrically erasable programmable read-only memory (not shown). Telephone units of this kind are known to those skilled in this art, and thus will not be described in detail.
The telephone unit includes a handset 4 having a keypad 5 as well as a speaker 6 and a microphone 7. A transceiver 8, ordinarily built into the telephone unit, exchanges signals via an antenna 10 with a mobile telecommunications switching office or MTSO 12 via a cell site 14. A duplexer 15 connects the antenna to the transceiver. The cell site 14 includes an antenna 16 connected to a control terminal 17 via a transceiver 18. The cell site 14 is connected to the MTSO via a transmission link 20. The Mobile Telephone Switching Office has historically been known as the center of the wireless over-the-air communications system. It is where the communication process management decisions are made, billing records are produced and where maintenance activities are initiated for wireless over-the-air communications systems. The MTSO is not a specific piece of equipment, but is comprised of many individual pieces. The MTSO will contain a telephone switch, peripheral processors, adjunct processors, and various other information gathering equipment used in the operation and management of a wireless over-the-air communications system. Each of the different pieces of equipment may directly or indirectly be involved providing the highest quality connection possible. The makeup of the MTSO therefore comprises many different pieces of equipment and many components, which can be supplied by different vendors. Therefore, communication process management decisions made at the MTSO can actually be made outside of a switch and can be made in a cluster of nodes housed along the network or even in separate cell sites. Therefore, as used herein the term MTSO really refers to all of the systems, nodes, modules, equipment and components that combine to define a wireless over-the-air communication process management network, regardless of the physical or system location of these elements. The term MTSO therefore is not intended to be limiting to the "switching off ice" as it may have been viewed in the prior art. The term is intended to be much broader than that and to include any combinations of equipment, etc that may be connected within the communication processing network of the service provider. The term MTSO is one of convenience and is intended to include all the information processing hardware and software associated with the wireless over-the-air communication process management process within a wireless over-the-air system, no matter where the hardware or software is located in the system. It is also noted that the term "intrasystem" refers to actions and components within a particular system; whereas, the term "intersystem" refers to actions and components located outside a particular system.
Referring to FIGS. 1 and 2, the operation of the CMR can be understood. The mobile unit M moves about the geographic areas covered by the various cells. As that mobile unit moves about, it decodes the overhead message control signals generated by various cell site control channels. The mobile unit locks onto the cell site that is emitting the strongest signal. The mobile unit rescans channels periodically to update its status. If, for example, a fixed-position land-based telephone T is used to call the mobile unit, a signal is sent via landlines L, to the central office CO of a public/switched telephone system (PTSN) 12A. This system then utilizes the switching network SN associated therewith to call the MTSO 12 via a transmission link L1. The MTSO then utilizes its own switching network and generates a page request signal to cell sites via transmission links, such as the transmission link 20. The cell site which has been notified of the presence of the mobile unit M sends a signal back to the MTSO via the landlines or wireless links alerting the MTSO of the presence of the mobile unit. The MTSO then orders the mobile unit, via the notifying cell site, to tune to an assigned channel and receive the communication process.
On the other hand, during communication process origination, the mobile unit rescans the control channels to determine which is the best server based on signal strength. Upon selecting the best server, the mobile unit transmits cell site information on the control channel receive frequency and then receives a voice channel to tune to if the mobile unit is authorized to place a communication process.
As the mobile unit moves, the signal strength between that mobile unit and the originating cell site changes, and perhaps diminishes. Since signal strength is an inverse function of the square of the distance between the mobile unit and the cell site, signal strength can change rapidly and drastically as the mobile unit moves with respect to the cell site and therefore must be monitored closely. The MTSO has a signal strength table, and signal strength from the mobile unit is constantly compared to acceptable signal strength levels in the table. Such a table can be located in each cell site if desired.
Should signal strength diminish below a preset range, the MTSO generates a "locate request" signal to all cell sites that neighbor the original cell site. Each of such neighboring cell sites receiving a signal from the mobile unit signals the MTSO, and the signal strengths from such neighboring cell sites are checked against the signal strength table. The MTSO makes a decision as to which cell site should control the communication process, and notifies the original cell site to order the mobile unit to retune to a voice channel of the new cell site.
As soon as the mobile unit retunes, the mobile unit completes the communication process via the new cell site channel. This transfer of control is known as a handoff.
Typically, governments grant rights to provide wireless communication services to a specified land area based on geographic boundaries. Since wireless propagation does not end at exact geographic boundaries, many conflicts have arisen between service providers as to which service provider should provide service at the location from where the Communication Process (CP) is being originated or received. Today, there are no methods or procedures to resolve these issues. A Communication Process (CP) can be defined as the exchange of information between communication devices, such as, but not limited to, Analog or Digital radiotelephones, digital data communications, analog or digital video, and the like.
When the initial wireless systems were built, they were constructed around major metropolitan areas. This created service voids between major metropolitan markets. In these early systems, boundary service problems did not arise because there were areas of "no service" buffering competing systems. Today, as rural systems fill in the patchwork of nationwide coverage, network service provision boundary disputes are becoming common. Prior to the Dennison, et al patent, U.S. Pat. No. 5,235,633 and the patents and applications depending therefrom as continuations and continuations-in-part, the disclosures of which are fully incorporated hereinto by reference, and the invention disclosed herein, it was impossible to honor the exact geographic boundaries. Attempts are currently made to control coverage boundaries by installing directional antennas and adjusting cell site receive and transmit parameters. The methods used to match the system boundaries to the geographic boundaries are not entirely successful due to the variations in terrain, environment and limitations of antenna design and wireless propagation. A common result of these problems is inadequate wireless signal strength or null coverage and border disputes around the geographic boundaries and hence poor service.
The incorporated material, including the Dennison et al patent disclose that cell sites sometimes have overlapping coverage due to the aforementioned variations in terrain and environment, and propose a solution. While the proposed solution works well, there is still room for further improvement in the areas of cost, subscriber service, billing and taxing.
Furthermore, wireless propagation, such as but not limited to the cellular operating band of 800-900 MHz, is generally line-of-site transmission. This presents substantial challenges when choosing sites in which to place wireless transmit/receive antennas. Boundaries assigned to service providers are based on maps depicting the geographic borders of service boundaries. The question arises in a disputed territory of who will get to service the Communications Process (CP). In the past, it has been the cell site that can provide the highest signal strength from the CD (Communications Device), not the provider that owns the legal territorial rights to the Communication Process (CP) that has serviced the Communication Process (CP). Until the invention disclosed herein, the service provider that could receive the best signal would handle the communication process (CP), and depending on whether the Communication Process (CP) was handed off and/or depending on the agreement made between the wireless communication systems, possibly keep all of the revenue from the communication process CP. Additionally, with real estate values being very high in established communities, cell sites are harder to construct and more expensive to build. Each cell site must be optimized for the maximum effective coverage area to overcome the real estate problems encountered when constructing a cell site. This in turn creates problems with overlapping coverage between wireless systems and thus disputes over which wireless system handles the communication process. Further, due to business considerations, it may be economically advantageous for one wireless system to own a cell site which is geographically located in the geographic area of another wireless system.
Cell sites are very expensive to install and maintain, so there is a very real savings for a service provider if fewer cell sites could be constructed while also improving coverage. Another area that would be affected by this is problems of quality service. This is because the service provider has conflicting requirements. To provide good coverage next to borders the provider would like to have high signal strength. To allow for hand-offs between cell sites and networks the signal strength needs to "fade out" at just the right level near the border to invoke a low threshold to start a hand-off process. It would be ideal to have high signal strength right up to a geographic boundary and then drop off beyond that boundary. However, at the present time, presently available systems do not permit this type of coverage.
Some areas inherently have wireless propagation problems, such as service areas next to bodies of water or in steep valleys. Wireless propagation can provide some very undesirable results for a number of reasons, some of which have been mentioned above and in the incorporated material. Therefore, there is a need to provide each network information as to which system has a right to handle a Communications Process (CP). For instance, a communications device (CD) might attempt to select a geographically incorrect service provider. Therefore, there is a need for a system that will permit a service provider to redirect the communication process to the geographically correct service provider, especially in a manner that is transparent to the Communications Device (CD) user.
Since cellular system geographic borders can be non-linear and can have irregular shapes, problems can arise. Problems associated with irregular boundaries are indicated in FIG. 3. FIG. 3 graphically shows the problem of obtaining coverage for areas that have irregular boundaries. In this figure, areas A and C are serviced by Carrier X, and area B is serviced by Carrier Y. It is noted that areas A and C are intrasystem with respect to Carrier X and area B is intrasystem with respect to Carrier Y, while areas A and C are intersystem with respect to Carrier Y and area B is intersystem with respect to Carrier X. It is also noted that areas A and B could be covered by just one cell site each but the overlap into adjacent territories would be difficult to resolve. Today, areas such as these would be split into two or more cell sites. For instance, Carrier X might elect to install three cell sites A1, A3 and A4 which provides a minimum of overlap into area B. Overlap is indicated at the shaded areas. Therefore, there is a need for a system what would allow Carrier X to install a cell site with a larger coverage area such as A2 (shown in dotted lines).
FIG. 4 shows a prior art attempt of providing sectored cells. Using prior art technology requires installation of directional antennas to minimize the overlap into neighboring territory in order to resolve a border issue. Since these antenna patterns cannot be made to follow curved geographic borders, sectors are installed and directed for the best geographic coverage possible. This often involves obtaining a cell site location close to the border and "shooting back" toward the wireless communication system's own territory. This can leave null zones where cells back onto each other in an effort to keep signals from overlapping into neighboring territory. These null zones will have either poor quality service or even no service at all, thereby resulting in poor service. Therefore, there is a need to overcome this problem as well.
FIGS. 5A and 5B illustrate a problem of how geographic terrain can affect prior art systems. In FIGS. 5A and 5B, a small rural network A is located just across the river from a large city C, which is part of a neighboring network B. The river defines the geographic and legal border between these two systems. The city C is in another state just across the river. In some river towns, there is a bluff on each side of the river. The network A can place their cell sites very near the border atop the bluff providing overlapping coverage into the city C. Network A will get all the service of the neighboring community D further away from the city C. Network A now has better line of cell site reception into the river valley with its corresponding traffic at river level than does network B who legally "owns" the territory. Network B would have to install additional cell sites in the river valley to obtain the same coverage. Due to the stronger signal level provided by Network A, Network A will process a communications process (CP). The result is that subscriber's Communication Process (CP) may not be processed by the correct service provider.
Note in FIG. 5A that there are two service providers X and Y. The intersystem boundary is shown as a dashed line down the middle of the river. With a bluff on either side of the river, the cells can only service the opposite bluff. This is shown where Y1 cell site cannot "see" the subscriber CD' hidden below. cell site Y1 can however find CD3 in service provider X's territory. This issue denies revenue to the wireless communication system that has legal right to serve the subscribers within its licensed geographic service boundaries. Prior art systems are incapable of determining the geographic location of both the communications devices and their service boundaries and thus compromise quality of coverage. Therefore, there is a need to resolve this issue.
There is also need for providing a wireless over-the-air communication system with the ability to adjust its coverage and billing as the mobile unit moves. This will permit the system to determine taxes based on where the communication process is actually being made as opposed to the criteria used with the prior art. Still further, there is a need to permit a wireless over-the-air communication system to change frequencies as the mobile unit moves whereby a single wireless service provider can provide service to its subscribers regardless of frequency.
Still further, due to various business reasons, a single cell site may advantageously be used by more than one system. It will be necessary to determine which wireless communication system bills the communication process. Prior art systems cannot fully account for this.
Still further, if there is a service problem with a mobile unit, prior art systems are not able to accurately identify the exact geographic location of the unit when the problem arose. This makes it difficult for the network to pinpoint coverage problems. Therefore, there is a need for a wireless over-the-air communication system that permits a wireless communication system to exactly and precisely identify the exact geographic location of a mobile unit when a communication problem occurs.
Still further, with the advent of emergency response networks that use telephones, such as the E-911 systems, there is a need for a wireless over-the-air communication system that can precisely locate a mobile unit and pass that information on to an emergency response system.
The location of an over-the-air system mobile unit making a communication process can also be of use to law enforcement agencies. However, signal strength from one cell site does not provide such location information with sufficient accuracy to be of the best assistance to law enforcement agencies. Therefore, there is a need for an over-the-air communications network that can provide geographic location of a mobile unit during a communication process with accuracy sufficient to satisfy law enforcement agencies. This information should be rapidly updatable so a mobile unit can be tracked.
Since the CMR industry is growing rapidly, competition is growing. Therefore, it is in the best interest of a system to be able to provide the best service possible to its subscribers. One way of achieving this objective is to customize the service to the exact needs of each subscriber. This can be achieved by, among other things, customizing and varying a billing rate plan for each subscriber. That is, the subscriber may be able to pay a lower rate when he is at work than he pays when he or she is at home. Therefore, there is need for a wireless over-the-air communication system that can vary rate plans and vary rates in a manner that will permit offering the best rate plan to each subscriber based on that particular subscriber's use and needs. Still further, some communication processes must be handled in a special manner to account for environmental conditions, or system needs, such as down time for a specific cell. Therefore, even if a communication process should be handled by a certain cell site, there may be times when that communication process must be handled by another cell site. Therefore, there is need for a wireless over-the-air communication system that can account for special circumstances associated with a communication process, and alter the system response when the mobile unit meets the criteria for those circumstances, even if the communication process is already in progress when the criteria are met.